Harry Potter fever is once again at a high following the release of the second film in the series, Harry Potter and the Chamber of Secrets. But with still no sign from JK Rowling that the fifth book is nearing completion, fans of the boy wizard may be getting desperate for some fresh adventures from the gang at Hogwarts.

Help is at hand in the form of fan fiction. In this curious literary genre that is flourishing on the net, fans of a particular book, TV series or film write their own stories using established characters and settings. Click on to http://fanfiction.net, the largest repository of fan fiction on the web, and you will find nearly 50,000 original stories written by Harry Potter addicts using Rowling's characters.

Quality control on such vast sites is variable, to say the least, so digging around for smaller, more specialised, sites is worth the effort. One of the legends of the Harry Potter fan fiction field is a 20-something New York journalist, Cassie Claire. Her novel-length HP stories can be found on http://schnoogle.com.

In one of the best of the genre, Draco Dormiens, she captures Rowling's style and cliffhanging chapter endings in an online book that promises "romance, mistaken identities, Really Cunning Plans, evil bake sales, a love triangle, and snogs galore". For a quicker fix of magic and muggledom, explore the larger site www.fictionalley.org, which offers a wealth of HP short stories, parodies and art.

Other stylish HP fanfic sites are http://Sugarquill.net, run by a group of young, professional, Harry Potter obsessives who beta-read all stories submitted to them for quality, and

While Harry Potter fan fiction has flourished on the net in the past couple of years, the genre predates Rowling's creation and its scope goes far beyond children's books. The site at http://fanfiction.net includes stories using characters from books, TV, movies, cartoons and comics.

On the TV front, cult series such as Buffy are a popular choices http://slayerfanfic.com, as are the X-Files and Xena: Warrior Princess. But the range of fanfic offerings is staggering, covering the gamut of TV drama and sitcoms from Allo Allo to the Young Ones.

Fan fiction grew out of the Trekkie phenomenon, with the first zine of fan fiction - Spockanalia - printed by Star Trek fans in 1967 .The site http://fanfiction.net alone has thousands of stories dedicated to the adventures of Spock, Scottie, and Captain Kirk.

Fan fiction can take on adult themes never encountered in the original books or films, and good fanfic sites will mark each story with a rating, based on the categories used by film censors.

Anything labelled NC17 may contain material of an adult, generally sexual, nature. "Shipping" - developing relationships between characters far removed from the author's original intent - is a common preocupation, and this reaches its apogee in slash fiction, a sub-genre in which homoerotic affairs between characters are explored. It is an idea born out of Trekkies' interest in the devotion between James Kirk and Dr Spock.

Unusually, most slash fiction features male/male relationships and is written by women, for a female audience. To dip a toe into these decidedly more adult waters, try http://beyonddreamspress.com.

The legal position of fan fiction can be murky, and some authors understandably dislike their characters being commandeered in this way. Anne Rice, for example, asked Fanfiction.net to remove all stories using her characters. A full exploration of this tricky area can be found at http://writersu.s5.com/law/copyright.html.

If reading fan fiction has inspired you to try writing your own, there are plenty of sites offering advice. Dr Merlin's Guide to Fan Fiction, written by respected fan-ficcer Melissa Wilson, is a good place to start.

According to Zsenya and Arabella of http://Sugarquill.net, fan fiction is ideal for inexperienced writers to hone their skills as it provides a ready-made world and characters. Unfortunately, inexperience, and, frankly, sheer inability, means that there is some truly dire fan fiction on the net. Godawful Fan Fiction is a site dedicated to documenting the depths to which the genre can descend, and bringing the "foulest fan fiction" to our attention. Hermione and the Pizza Boy, anyone?